In recent years, stirling engines which have an excellent theoretical thermal efficiency attract attention as means for recovering exhaust heat of factories or exhaust heat of internal combustion engines mounted on vehicles such as passenger cars, buses, and trucks.
One known technique is described in Japanese Patent Application Laid-Open No. 2000-46431 (Patent Document 1) which discloses a piston apparatus which is applicable to an external combustion engine such as a stirling engine. A piston of an external combustion engine disclosed in Patent Document 1 is such a type that is applicable to a stirling engine provided with a displacer driven by the function of a working medium which repeats compression and expansion within a working space according to reciprocating movements of a piston in a cylinder. The piston apparatus includes a compression chamber which is formed inside the piston to temporarily store the working medium compressed in the working space, an orifice through which the working medium in the compression chamber is ejected to a clearance between the piston and the cylinder, and a check valve which is arranged at an end of the orifice at the side of the compression chamber. The check valve is arranged so as to prevent a back-flowback-flow of the working medium from the compression chamber to the working space at a time the pressure of the working medium in the working space is decreased due to the movements of the piston.
Patent Document 1: Japanese Patent Application Laid-Open No. 2000-46431